When fabrics are washed they acquire a rougher texture which feels harsh to the skin. Cotton fabrics are particularly affected. To counteract this, many consumers add fabric softening compositions to the rinse water. These fabrics softening compositions are generally an aqueous dispersion of material with a cationic head group and 1 or 2 alkyl chains which are attached to the head group and are of sufficient length to make the cationic material insoluble in water. This cationic material is then deposited on the fabric, and causes the fabric to have a softer feel.
Fabric softening can also be carried out in a tumble dryer. For this, the consumer uses a sponge, porous sheet or other article which has been impregnated with a cationic fabric softening agent similar to those used in an aqueous dispersion.
There have also been proposals to formulate a detergent composition so that a fabric softening effect is provided during the washing of the fabrics rather than during a rinsing step. Such softening can be accomplished using certain clays which have ion exchange properties. It has also been proposed to use certain nonionic materials to give fabric softening during washing.
U.S. Pat. No. 5,401,426 discloses that certain lactobioamides, which are nonionic surfactant materials contain a single C14 to C18 alkyl or alkenyl chain, may be used as softening agent in a rinse conditioner composition.
GB 1409416 discloses that sucrose distearate may be included in a combination of fabric softening agents in a rinse conditioner composition.
U.S. Pat. No. 3,598,865 discloses the manufacture of surface active alkyl glycosides by reacting a monosaccharide or a compound hydrolysable to a monosaccharide with a monohydric alcohol having from 8 to 25 carbon atoms. It is mentioned that this alcohol may be primary or secondary, straight or branched chained. It is also briefly mentioned that the glycosides may be used for a variety of purposes including textile softeners. The document does not give guidance for more specific selection of alkyl glycosides for use as textile softeners.
GB-A-2185991 teaches a detergent composition in which fabric softening is provided by the incorporation of an alkyl glycoside. GB-A-2185992 discloses detergent compositions which contain an alkyl glycoside jointly with a quaternary ammonium compound and other materials. In both of these documents the alkyl glycoside is broadly defined as having 1 or more hydrophobic groups containing 1 to 30 carbon atoms per hydrophobic group, and a hydrophilic glycoside group. Preferred alkyl glycosides are described as having a single alkyl chain.
EP-A-380406 discloses a detergent composition containing anionic and nonionic surfactants together with a sugar ester as a fabric softening agent. The sugar ester is defined as containing at least one fatty acid chain.
We have now found that fabric softening can be achieved using a product in which the fabric softening agent is one or more organic compounds which are free of cationic quaternary nitrogen groups and bear two hydrophobic aliphatic chains attached through a linking group to a polyhydroxylated, hydrophilic head group. The compound(s) are preferably substantially nonionic.
The present invention is thus able to provide compositions in which fabric softening can be achieved without the use of quaternary ammonium materials, or with a reduced content of such materials.
Rinse conditioner formulations which contain a cationic fabric softening material are generally formulated as aqueous dispersions. It is not a simple matter to formulate an aqueous dispersion which will be stable during storage under varying temperatures, possibly even including exposure to temperatures below freezing. For some markets it is desired or required to use a fabric softening agent which is biodegradable. For quaternary ammonium fabric softeners this has been achieved by the use of materials containing an ester linkage but it is then necessary to guard against hydrolytic instability of the ester linkage, (which is the subject of European Patent 239910).
The use of a non-quaternary fabric softening material in accordance with the present invention can assist in the formulation of a product which is storage stable. Some forms of the fabric softening material can provide biodegradability without problems of hydrolytic instability.
Further advantages of a composition based on non-quaternary material are that it will avoid interfering with detergency when the fabrics are next washed with a detergent composition containing anionic detergent; it can assist perfume delivery, and can factilitate the preparation of concentrated products with good physical stability, even when subjected to low or high temperature.